I. Field of the Invention
The present invention relates generally to trackside or in track railway car handling equipment for positioning railcars along a track for loading or unloading operations. More particularly, the present invention relates to a ratcheting train positioning system that employs a tandem dog carriage arrangement between the rails that enables force to be applied serially by one dog at a time to consecutive railcar trucks to move a string of railcars to position consecutive railcars for loading or unloading without exceeding the maximum force allowable on any one railcar.
II. Related Art
Freight-hauling railway cars need to be precisely positioned proximate freight or cargo handling equipment to undergo loading and unloading operations. Freight in the form of bulk cargo such as grain is typically loaded or unloaded with reference to stationary freight handling equipment such as chutes and conveyor equipment situated at fixed locations above or in pits beneath a specific dedicated portion of the track. Railcars for transporting grain or other such finely divided dry bulk agricultural commodities may be covered and designed with a plurality of spaced bottom discharge hopper bins or chutes accessing the main cargo storage volume. The chutes are closed by capstan-operated rack and pinion bottom closure gate systems.
In the loading and discharge operations, a connected engine roughly positions one end of a string of cars to be loaded or unloaded beneath or above the appropriate equipment at the desired fixed location. Because locomotives are not well suited for precisely positioning individual cars or even strings of cars along a railroad track, positioning devices known as train movers or positioners are located at fixed stations along the track. The positioning devices generally employ heavy pushing members known as railcar-engaging “dogs” to move the cars into position.
Positioning devices generally classified in the industry as “indexers” position railcars using dogs to push against railcar bogey frames or axles. Bogey frame indexers may employ dogs carried by a pair of carriages operating along indexer tracks on built-in guideways located on opposite sides of associated track rails. Indexers are designed so that the carriages and associate dogs on both sides of the track are coordinated to operate together in unison to engage and move a car or string of cars along the track. Thus, in indexer type bogey frame-engaging positioning devices, dogs on opposite sides of the track are caused to engage the bogey frame during the same stroke to thereby provide a balanced force by pushing against both of the spaced sides of the truck bogey frame simultaneously. Axle-type indexers include carriages operated between the tracks that employ a single central dog to engage truck axles rather than bogey frames. The indexer system of the invention is an axle-type indexer.
While each type of railcar indexer has certain advantages, an axle system does not require guideways located outside the track rails and can conveniently be used with automated railcar discharge gate equipment, for example. The use of a single, centrally located guideway simplifies the system and it would be even more advantageous if the system could be operate using a single hydraulic cylinder in a ratcheting manner to advance a string of cars.